In our current game two bits of road have joined to become one road, and there are two meeples of the same colour on that stretch. Once the road is completed how is it scored... does the player get two lots of points for the road or one lot of points. I can't see this clarified in the rules.

Meeples are used to determine who gets the points, not how many points are given. You'll get the same points whether you have 1 meeple or all of your meeples on a feature when you're the only one on it. If someone else is also on the same feature, then whoever has more gets the points. If you tie, then you both get the full points (they are not split).

If there is 1 meeple of yours and 1 meeple of someone else that have started 2 separate roads, and then they have merged together, then you and your opponent get full points. If the total points for the road were 8 points, you would get 8 and your opponent would get 8.

If you had 1 meeple and your opponent had 2 meeples (excluding builder) then you would get 0 points and your opponent would get 8 points.